Exercise machine



FIG. 1 is a left front perspective view of an exercise machine showing our new design;

FIG. 2 is a right front perspective view thereof;

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a right side elevational view thereof;

FIG. 5 is a front view thereof; and,

FIG. 6 is a rear view thereof. 

The ornamental design for an exercise machine, as shown. 